1. Field of the Invention
The invention is in the field of blood sample acquisition and testing. In particular, the invention is directed to a sensor strip positioning mechanism used in a device that performs both a lancing operation to acquire a blood sample and a measurement operation on the sample in one user-initiated step. The strip is provided with a plurality of test sites, wound on a supply wheel and fed through the device between the supply wheel and a take-up wheel, so that a single strip may be used to obtain a plurality of measurements. According to the invention, a mechanism is provided to control the advancement of the strip in precise increments for proper alignment of the test sites in the device.
2. Description of the Related Art
Self-monitoring of blood glucose generally requires the user to extract a volume of capillary blood and place it on a disposable element for analysis. Devices for lancing a subject at an extraction site to obtain a small quantity of blood for testing on a test strip are known in the prior art. For example, U.S. Pat. No. 6,558,402, which is incorporated by reference, discloses a lancer having mechanisms for piercing a subject's skin and obtaining a sample.
Test strip sensing elements using amperometric and other techniques for determining the concentration of blood glucose in a blood sample are known in the prior art. U.S. Pat. Nos. 6,143,164, and 5,437,999, incorporated by reference herein, each disclose examples of test strip construction for electrochemical measurement of blood glucose.
The integration of lancing and sensing would be a desirable advance in the self-monitoring of blood glucose. U.S. patent application Ser. No. 12/502,594, filed Jul. 14, 2009, which is incorporated by reference, describes such a “two-in-one” device, wherein a single test strip contains a plurality of test sites, which can be advanced automatically through a testing device. Application Ser. No. 12/502,585, also filed Jul. 14, 2009 and incorporated by reference, describes fluid transport features that may be included on a continuous strip to facilitate the movement of a blood sample from the collection site to the test site. U.S. patent application Ser. No. 12/689,654 filed Jan. 19, 2010, and incorporated by reference, discloses an electrode layout on a continuous test strip which makes electrical contact with contacts in a device, producing signals which are used to control the advancement of the sensor strip. In this context, it would be desirable to have a mechanism to permit automatic advancement of the strip through the device in precise increments, that would account for changes in the effective diameter of the supply wheel and take-up wheel as the sensor strip is wound from one to the other as the strip is indexed through different stop points in the lancing/sensing process.